Congressional Republicans may have cost Susan Rice a job as secretary of state, but President Obama has now given her a post that could be more powerful.

In moving Rice from United Nations ambassador to national security adviser, Obama said Wednesday that she "exemplifies the finest tradition of American diplomacy and leadership."

She also assumes a job designed to coordinate national security policies along with the State Department, Pentagon and intelligence agencies — a very influential position within what one analyst called a "White House-centric" administration.

"It's driven by the very small group of people close to the president," said David Rothkopf, CEO and editor-at-large of Foreign Policy magazine.

Rice — a long-time adviser to Obama — "is already a member of that group," Rothkopf said.

The Rice appointment renewed Republican accusations that Obama administration officials sought to cover up details of the Sept. 11 attack on a U.S. facility in Benghazi, Libya. The protests have little effect, however — the national security adviser's job does not require Senate confirmation.

Obama also announced Wednesday that he is nominating former National Security Council aide Samantha Power to replace Rice at the U.N., describing the human rights scholar as "one of our foremost thinkers on foreign policy."

Unlike national security adviser job, the U.N. position does require Senate approval.

Rice, 48, will replace Tom Donilon, whose work as national security adviser since 2010 won praise from a president who spoke of " strengthening our alliances" and "enhancing our relationship with key powers."

The switch comes as Obama prepares for a summit with Chinese President Xi Jinping; Donilon was in Beijing recently preparing for the meeting.

Donilon, 58, will stay on the job until early July, working with Obama on planned trips to Europe and Africa.

His retirement has been expected sometime this year, and Rice has long been considered the top candidate for his replacement.

Obama had considered Rice for secretary of State late last year, but appointed John Kerry instead, in part because of the controversy that surrounding the Benghazi attack that killed four Americans, including U.S. ambassador Christopher Stevens.

Republicans investigating Benghazi have criticized Rice over television interviews she gave five days after the attack, attributing it to protests over an anti-Islam film. After the administration later called it a pre-planned terrorist assault, GOP members accused Rice and others of an attempted cover-up.

Rice said she discussed the attack based on the evidence known at the time, while Obama and aides accused the Republicans of politicizing the tragedy.

Sen. Rand Paul, R-Ky., a potential 2016 presidential candidate, tweeted after Rice's appointment: "I really question the President's judgment in promoting someone who was complicit in misleading the American public on the Benghazi attacks."

The Rice appointment may also be a sign that Obama and aides believe the Benghazi investigation is behind them.

"It is certainly a very confident move on the part of the president," Rothkopf said.

During a Rose Garden ceremony unveiling his revamped team, Obama noted that Rice put together his foreign policy advisory team ahead of the 2008 presidential campaign.

Describing Rice as "passionate and pragmatic," Obama said that "everybody understands Susan is a fierce champion for justice and human dignity. But she's also mindful that we have to exercise our power wisely and deliberately."

In brief remarks, Rice said she was "deeply honored" by the appointment, and added that "we have vital opportunities to seize and ongoing challenges to confront."

Among those challenges: The U.S. reaction to the civil war in Syria and violence throughout the Middle East, sometimes testy relationships with China and Russia, and completing the end of U.S. combat operations in Afghanistan.

James Mann, author of a book on the administration's foreign policy team called The Obamians, said the national security adviser is often "more central" to policy making than the secretary of state, especially in this White House.

"I think Obama wants to be his own decision maker on foreign policy," said Mann, author-in-residence with the School of Advanced International Studies at Johns Hopkins University.

One Republican critic — Sen. John McCain, R-Ariz., Obama's opponent in the 2008 presidential election — tweeted that while he disagree with the Rice appointment, "I'll make every effort to work with her on important issues."

In nominating Power to be the new ambassador to the United Nations, Obama picked a former campaign aide, White House official and author who has specialized in genocide and human rights. As Obama noted, Power, 42, won a Pulitzer Prize for her 2002 book, A Problem From Hell: America and the Age of Genocide.

Power had to leave the presidential campaign in the spring of 2008 after describing then-rival Hillary Rodham Clinton as a "monster" who would stop at nothing to defeat Obama. Power apologized for the remark. After the election, Obama put Power on the NSC and made Clinton his first secretary of State.

Power, who was born in Ireland, said the United States plays a critical role in helping the United Nations meet its obligations. "I have seen U.N. aid workers enduring shell fire to deliver food to the people of Sudan," she said. "Yet I've also seen U.N. peacekeepers fail to protect the people of Bosnia."

Donilon has worked for Obama throughout his presidency, first serving as deputy national security adviser. Obama appointed him to the top job in October of 2010, following the departure of James Jones.

Obama said Donilon helped improve U.S. relations with Asia, wind down the wars in Iraq and Afghanistan, slap new sanctions on Iran, and coordinate the raid that killed 9/11 architect Osama bin Laden in 2011. The president said Donilon handled a wide portfolio that ranged from trade to energy to military security. "Tom has been instrumental every step of the way," he said.

For his part, Donilon praised Obama and thanked him for his appointment, calling it "the privilege of a lifetime."